-LRB- CNN -RRB- -- Australian authorities ended their efforts to find survivors Friday after a boat carrying scores capsized off the coast of Indonesia this week .

An Australian naval ship and four merchant vessels rescued 55 people in an area west of the Indonesian island of Java , the Australian Maritime Safety Authority said . But many more others may have perished in the sea .

The authority said it was halting further efforts following medical advice that `` there is no realistic prospect of survivability . '' One body was recovered during the rescue operation .

Rescuers had been searching for survivors since Wednesday , when Australian authorities received a call from someone aboard saying the vessel was having engine trouble . The caller said it had about 150 people aboard , presumed to be asylum seekers .

The survivors , including at least three with injuries , were being taken to Merak , Indonesia , Australian authorities said .

Several ships carrying asylum seekers in Australia have run into trouble in the waters between Indonesia and Australia in recent years .

Read more : Asylum seekers risking all to escape dangers of home

Vessels often head for Christmas Island , a remote Australian territory closer to Java than to the Australian mainland .

Dozens of people are believed to have died after two ships capsized near Christmas Island in June . More than 200 people were rescued from those accidents .

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The 55 survivors are headed to Merak , Indonesia

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Rescuers have been searching since Wednesday after a boat reported engine trouble

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Australian authorities say there is `` no realistic prospect '' of other survivors

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Ships carrying asylum seekers in Australia regularly run into trouble in the area